The present invention relates to a disc apparatus for writing, reading, etc., to and from a disc such as a CD (Compact Disc) and a DVD (Digital Versatile Disc). Particularly, this invention relates to a disc apparatus operable to restict disc floating due to motor rotation.
Disc apparatuses are known in use for writing, reading, etc., to and from a disc such as a CD and a DVD with an optical pickup while an installed disc is rotating at a high speed. The disc is set by a clamp mechanism on and rotated on a turntable that is rotated by a turntable motor.
In such a disc apparatus, when a disc is rotating at a high speed of 8,000 rpm or higher, air near the disc surface is also rotating and flowing from the disc inner to outer sections due to a centrifugal force. This airflow causes decrease in air pressure over the disc inner section, which could force the disc to float over the turntable. A larger force to make disc floating than a damping force by the clamp mechanism could force the disc to be released from the turntable against the clamping force.
A technology to avoid such disc floating is disclosed, for example, in Japanese Unexamined Patent Publication No. 2001-250301. Illustrated in FIG. 14 is a top plate (shielding member) 102 that covers the housing of a disc apparatus disclosed in this document. FIG. 14 shows the surface of the top plate 102 that faces the upper surface of a disc 2. The top plate 102 is provided with several arc protruding members 104 from the disc inner to outer sections. The protruding members 104 force air to flow from the disc outer to inner sections to restrict decrease in air pressure over the inner section, thus restricting disc floating.
The inventor of the present invention examined this technology and found out that disc floating cannot be restricted enough unless the configuration of the protruding members 104 is optimally determined. In detail, decrease in air pressure over the disc inner section depends on the height and/or the number of the protruding members 104, a gap between the disc 2 and the members 104, etc., which could result in insufficient floating restriction.